The MS2000 shows "IPL s.p.u [ ]" in the LCD when it is powered on, as if it is in OS update mode.

If I try using the Korg v1.07 updater, the LCD display changes to "IPL s.p.u [hrd]" and the updater then shows the "Receive Error(timeout)" message.

If I boot up the MS2000 using one of the diagnostic modes, e.g. with the mod seq on/off and patch 1 buttons pressed while turning on power, the LCD shows "KORG MS2000" for a while, then comes up showing Patch A0 in the LCD.

In this mode, no sound is heard from the headset jack, but patches can be changed using the buttons and different LEDs light up on the panel, as if everything else is working.

The synth is also sending Midi keyboard and control and program change messages out over channel 1.

I've cleaned and reseated all internal connectors to the PCBs inside the synth.

I'd welcome some suggestions and/or thoughts on what the problem might be, and what to try next